1. Field of the Invention
The present invention relates to a steering system for a vehicle. Especially, the present invention relates to the steering apparatus for transmitting an operational (steering) force of a steering wheel to a tire-and-wheel by way of a cable unit.
2. Description of the Related Art
Japanese Patent Unexamined Publication No. JP2000028451 (JP00028451) discloses a steering apparatus for a vehicle. For securing free layout and the like of the steering apparatus, a cable unit is so constituted that a torque is transmitted by pulling a cable wire. The cable unit is disposed on a steering force transmission path between a steering wheel and a tire-and-wheel.
FIG. 18 and FIG. 19 show a schematic of the steering apparatus according to Japanese Patent Unexamined Publication No. JP2000028451 (JP00028451). The steering apparatus is constituted of a steering column, a cable unit 3, and a power steering unit 5. The steering column has a steering shaft 2 connected to a steering wheel 1. A rotational force of the steering shaft 2 is transmitted to the cable unit 3. In accordance with the rotational force transmitted from the cable unit 3, the power steering unit 5 gives the steering force, by way of a rack-and-pinion gear 4, to a front right tire-and-wheel WR and a front left tire-and-wheel WL.
The cable unit 3 is constituted of an output pulley 6, an input pulley 7, a cable 8, and a cable 9. The output pulley 6 is received in a housing 10A, and is connected to a peak end section (upper in FIG. 19) of the steering shaft 2. The input pulley 7 is disposed on a side having the power steering unit 5, and is received in a housing 10B. The cable 8 has an outer tube 8a and a cable wire 8b. The cable wire 8b is slidably disposed in the outer tube 8a, and has a first end connected to the output pulley 6 and a second end connected to the input pulley 7. The cable 9 has an outer tube 9a and a cable wire 9b. The cable wire 9b is slidably disposed in the outer tube 9a, and has a first end connected to the output pulley 6 and a second end connected to the input pulley 7.
As is seen in FIG. 19, the output pulley 6 is substantially perpendicular to an axial direction of the steering shaft 2 which is axially connected to the output pulley 6. The peak end section of the steering shaft 2 is born with a bearing 11 and a bearing 12 which are supported in the housing 10A. Moreover, a first end 8c of the cable wire 8b and a first end 9c of the cable wire 9b are wound around a cable winding groove (quintuple) formed on an outer periphery of the output pulley 6. On the other hand, the rack-and-pinion gear 4 is connected at an end of a spindle (not shown) which is fixed to a center of the input pulley 7.
The power steering unit 5 which acts as a power assistant means is supported to the housing 10B. In the housing 10B, an output shaft (not shown) is formed with a worm (not shown) which engages with a worm wheel (not shown) formed on a rotation shaft (not shown). Thereby, a torque of the power steering unit 5 is transmitted to the rotation shaft (not shown), by way of the worm (not shown) and the worm wheel (not shown).
Turning the steering wheel 1, for example, clockwise turns the output pulley 6 clockwise by way of the steering shaft 2. Then, one (cable wire 8b) of the cable wire 8b and the cable wire 9b is wound and pulled, to thereby turn the input pulley 7 counterclockwise. With this, the rack (of the rack-and-pinion 4) slides leftward, to thereby steer the front right tire-and-wheel WR and the front left tire-and-wheel WL rightward.
Simultaneously with the above, the other (cable wire 9b) of the cable wire 8b and the cable wire 9b is loosened and wound around the input pulley 7. Turning the steering wheel 1 counterclockwise causes an opposite operation to the on described in the above two paragraphs.
The steering apparatus (for the vehicle) according to the above related art, however, sets a steering angle of the steering wheel 1 equal to a winding angle (or winding length) of the following two members: The cable wire 8b wound by means of the output pulley 6 and the input pulley 7. The cable wire 9b wound by means of the output pulley 6 and the input pulley 7. In other words, the number of grooves for winding the cable wire 8b and the cable wire 9b is set equal to the number of revolutions of the steering wheel 1. Therefore, the number of grooves (for winding the cable wire 8b and the cable wire 9b) is relatively large.
Accordingly, the output pulley 6 and the input pulley 7 are large in width W (FIG. 19). As a result, an enough space is not secured for a driver around his/her legs especially where the output pulley 6 is disposed.
The output pulley 6 is directly connected to the steering shaft 2. Thereby, the above perpendicularity of the output pulley 6 to the steering shaft 2 is unavoidable, to thereby restrict freedom of layout.